1. Field of the Invention
The present invention relates to a canister applied to a motor vehicle to reduce the discharge of fuel gas and, more particularly, to a canister for a motor vehicle which can significantly reduce the amount of discharged fuel gas.
2. Description of the Prior Art
As is well known in the art, a motor vehicle has a device for storing fuel gas generated in a fuel tank and then supplying the fuel gas to an engine. This device is commonly called a canister.
In general, fuel to be used for driving the engine is stored in a fuel tank. In the fuel tank, as the fuel vaporizes due to environmental factors such as the surrounding temperature, fuel gas is generated. Because the fuel gas contains noxious constituents, if the noxious constituents are discharged out of the motor vehicle, air pollution and waste of fuel result.
In the canister, while the engine is stopped, the fuel gas generated in the fuel tank is adsorbed and stored by activated charcoal, and then, when the engine is started, the stored fuel gas is supplied to the engine, whereby air pollution and the waste of fuel are prevented. This type of canister has been disclosed in Korean Unexamined Patent Publication Nos. 2004-90740, 2004-17053, 2003-89139 and 2001-36538.
FIG. 1 is a systematic view schematically illustrating the connection between a canister 1 and a fuel tank 2.
Referring to FIG. 1, an inlet pipe 3 of the canister 1 communicates with the fuel tank 2. With the engine stopped, the fuel gas generated in the fuel tank 2 is introduced into the canister 1 through the inlet pipe 3 due to the internal pressure of the fuel tank.
Activated charcoal for adsorbing the fuel gas is charged in the canister 1. The fuel gas introduced into the canister 1 through the inlet pipe 3 is adsorbed by the activated charcoal. Of course, in this case, the remnant of the fuel gas, which is not adsorbed by the activated charcoal, is discharged to the atmosphere through an outlet pipe 4 which is connected to the canister 1.
The canister 1 and a throttle pipe 6 communicate with each other via a guide pipe 5. A control valve 7 is installed on the guide pipe 5 to control the flow of fuel gas from the canister 1 to the throttle pipe 6. The control valve 7 is closed with the engine stopped and is opened with the engine started.
When a driver starts the engine, air is supplied to the engine through the throttle pipe 6. In this state, since the internal pressure of the throttle pipe 6 is lower than atmospheric pressure, outside air is introduced into the throttle pipe 6 through the discharge pipe 4, the canister 1 and the guide pipe 5. At this time, the fuel gas which is adsorbed by the activated charcoal in the canister 1 is introduced into the throttle pipe 6 along with the air flow and is supplied to the engine.
The conventional canister suffers from a drawback as described below.
According to recent regulations limiting the discharge of fuel gas, that is, regulations mandating a PZEV (partial zero emission vehicle), the discharge of fuel gas must not exceed 0.35 g per gallon of fuel.
In this regard, the conventional canister encounters problems in that the inside structure thereof is not appropriate for accommodating various kinds of activated charcoal, and since the flow path of fuel gas is simple, fuel gas cannot be sufficiently adsorbed to the activated charcoal. That is to say, the conventional canister cannot satisfy the PZEV regulations due to its structure.
Further, in order to respond to these problems, while attempts have been made to separately attach a fuel gas reducing device capable of reducing fuel gas outside the canister, in this case, a problem is caused in that, since the fuel gas reducing device, which is expensive, must be added, the manufacturing cost of the motor vehicle markedly increases.